Optical Performance

The Tokina 12-24 doesn’t disappoint. Full aperture results at 12mm are excellent, especially for this class of lens, and well up to the standard of either the Nikon or Canon lenses, with very good resolution of fine detail right into corner shadow areas, which really is exceptional for this wide a lens at full aperture. Field curvature is noticeable towards the edge of the frame - but distortion is to an extent what this sort of lens is about. Distortion levels look about the same as the Canon EF-S 10-22 but I think less than the Nikon DX 12-24, although I couldn’t make a direct comparison. 

At 18mm and 24mm full aperture performance is still excellent, with perhaps a little more fall off in the extreme corners, but really that’s splitting hairs. Over most of the field a surprising amount of fine detail is recorded, and even almost in the corners larger objects have very high edge sharpness, just very slightly less fine detail. A tiny amount of CA is visible at the edges at 18mm, very slightly more at 24mm, but barely noticeable in both cases, even at 100%, so in real life I wouldn’t consider it significant.

Stopping down even one stop to f5.6 bring an even higher level of performance right through the zoom range - images are very slightly crisper, and the small amount of CA in the corners is now barely visible.

Lens tested with a Canon EOS 20D.